Bicycle brake system

ABSTRACT

A hydraulic brake system for a two wheel bike having handlebars, a master cylinder assembly mounted on the handlebar, the assembly including a housing, a tubular body mounted in the housing, a piston mounted in the tubular body, an overrating lever pivotally mounted on the housing, a push rod operatively connecting the operating lever to the piston, a spring mounted in the cartridge body to bias the piston to an inoperative position in the cartridge body, a resilient bladder filled with a hydraulic fluid enclosing the cartridge body, a port timing hole in the cartridge body connecting the cartridge body to the bladder to maintain fluid pressure in the cartridge body, a brake assembly mounted on the housing, and a brake line operatively connecting the cartridge body to the brake assembly.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 08/920,495,entitled BICYCLE BRAKE SYSTEM, filed Aug. 29, 1997.

FIELD OF THE INVENTION

The present invention relates to a bicycle brake assembly, and moreparticularly to a closed bladder system which prevents the admission ofair into the hydraulic brake system even though the bicycle is upsidedown.

BACKGROUND OF THE INVENTION

Bicycle brakes have evolved from hub brakes on rear wheels to machinedcantilever brakes on front and rear wheel rims to disk brake systems.Many conventional disk brake system designs are not suited well to thebicycle, particularly since the bicycle will be operated by bothchildren and adults, will be flipped upside down and laid on its sideand made to be extremely light in weight. Current attempts at adaptingmotorcycle and automotive hydraulic disk brake technology to bicycleshas fallen short due to this market's peculiar needs.

SUMMARY OF THE PRESENT INVENTION

The brake system described herein innovates a bleedable fluid reservoirwith a bladder system that allows the atmospheric pressure reservoir tobe drawn upon allowing the brake caliper piston to self adjust for padwear without the potential of air ingestion and with room to expand thefull volume in a high brake temperature condition. This system adapts athermally compliant brake disk concept to an extremely lightweightembodiment for the bicycle industry yielding high torque carryingability along with unparalleled thermal durability in a one piecedesign.

The system uses a ball joint piston design as shown in U.S. patentapplications Ser. No. 08/638,526, entitled "Ball Joint Piston," and Ser.No. 29/044,276, entitled "Heavy Duty Brake Disc," to allow the smallestpackaging for low weight and good wheel spoke clearance as well aseliminating the possibility of brake drag. This system demonstrates auser friendly lever adjustment to allow hand sizes from those ofchildren to adults for comfort and safety. This lever adjustment avoidsrattles and vibration effects with a rod back stop that reduces criticaltolerances and whose piston and boot grip the mating push rod.

A unique post and piston assembly is coupled to a friction pad backingplate that uses a wire formed spring to secure the friction pad whichboth maximizes the disk to friction material clearance (eliminating anybrake drag) while allowing an extremely easy pad change. This padretention system also prevents the pads from falling out whiletransporting the bicycle with the wheel (and therefore the brake disk)out of the front fork. This system also prevents rattling noise byholding the friction pad backing plate tightly to the face of the brakepiston.

Other principal features and advantages of the invention will becomeapparent to those skilled in the art upon review of the followingdrawings, the detailed description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of the master cylinder shown mounted onthe handlebar;

FIG. 2 is a cross-section view of FIG. 1 showing the adjustable push rodassembly (piston reservoir bladder, bleeder and compression fitting);

FIG. 2A is an enlarged view of the ball end and snap ring arrangement;

FIG. 2B is an enlarged view of the port timing opening and the fluidcompensating openings;

FIG. 3 is an external view of the reservoir bladder in its free state;

FIG. 4 is a view of a piston and an angular attitude to the caliperbore;

FIGS. 5 and 6 show the contrast in spoke angle achievable with standardpistons versus the ball joint piston to bore geometry;

FIG. 7 is a perspective view of the pad spring;

FIG. 8 is a perspective view of the piston;

FIG. 9 is a perspective view of the friction pad and plate assembly;

FIG. 10 is a cross-section view of the brake caliper assembly;

FIG. 11 is a view of the brake pad partially installed in the housingshowing the deflection of the pad retention spring;

FIG. 12 shows the beveled top of the pad ramped over the piston post;

FIG. 13 shows the pad partially removed from the housing disk slot;

FIG. 14 shows the thermally compliant brake disk; and

FIG. 15 is a cross-section view of a fixed pad single acting caliperassembly.

Before explaining at least one embodiment of the invention in detail itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments or being practiced or carriedout in various ways. Also, it is to be understood that the phraseologyand terminology employed herein is for the purpose of description andshould not be regarded as limiting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The master cylinder assembly 1 as shown in FIGS. 1 and 2 includes anouter housing 2 and an inner cylindrical body 4 (i.e. cartridge body 4)mounted in the outer housing 2. A containment ring 8 is mounted on oneend of the housing 2 for supporting one end of the cylindrical body. Arubber reservoir bladder 3 as shown in FIG. 3, has one end sealed to theinner end of the cylindrical housing 2 by a seal ring 3A and the otherend secured to the containment ring 8 by the housing 2. An air space 53is provided between the bladder 3 and the housing 2. The cylindricalbody 4 is mounted in a spaced relation from the bladder 3 to form afluid reservoir 5. A bleeder screw 6 is mounted in a threaded bleederport or hole 16 in the containment ring 8 and sealed therein by anO-ring seal 7. A piston 9 is axially aligned in the cylindrical body 4and retained therein by means of a snap ring 32. A spring 62 is alignedwith the piston 9 to bias the piston to the open position in contact tothe snap-ring 32. A primary cup seal 10 is aligned in a groove 10A inthe end of the piston 9. Referring to FIG. 2B a port timing hole 11 isprovided in the cylinder 4 downstream from the cup seal 10. A fluidcompensating hole 12 is provided in the cylindrical body 4 upstream fromthe groove 10A. A secondary cup seal 13 is aligned in a groove 13A inpiston 9 upstream from fluid compensating hole 12.

The cross-section of the housing 2 shown in FIG. 2 shows the state ofthe bladder 3 in a normal operating position. The bladder 3 is filledwith fluid from the brake bleeder valve 70 as shown in FIG. 10 and isdevoid of air. The air space 53 is provided outside the bladder 3 toallow for fluid expansion of the bladder that occurs during heavybraking as the fluid is heated. There is adequate reserve fluid volumewithin the bladder 3 to allow for brake piston adjustment outward tocompensate for brake pad wear. The system is designed to provide the airspace 53 between the bladder 3 and the housing 2. The fluid volume ofthe bladder 3 is determined by virtue of the shape of the bladder 3.

In this regard a perspective view of the bladder 3 is shown in FIG. 3 inits free state. The side walls of the bladder 3 are provided withindentations or dimples 54 which allow the bladder in the housing 2 tocompensate for the expansion and contraction of the brake fluid.

Referring to FIG. 2, the system filling process is shown wherein brakefluid enters the cartridge body 4 from the brake line 14 through aninlet 15 formed at the end of the cartridge body 4. A threaded connector52 is mounted on the threaded end 50 of the housing 2. A threaded cap 51matingly engages the outer threaded end of connector 52. A seal 56 isprovided on the inner end of connector 52 to seal the end of the brakeline 14. The spring 62 is seated in the threaded end of the cartridgebody 4.

The brake fluid flows through the timing port 11 carrying the system airwith it and filling the bladder 3 with fluid. The air in the bladder 3flows out through the open bleeder port 16. As this flow continues allair trapped in the system is exhausted out of the bleeder port 16. Aslight flow restriction at the bleeder port 16 causes a slight fluidpressure rise which expands the dimples 54 in the bladder 3 outwardly.When the fluid source is shut off, the bleeder port 16 in thecontainment ring 8 is left open to allow the bladder 3 to relax into itsoriginal shape as shown in FIG. 3, exhausting a slight amount of fluidout through bleeder port 16. The bleeder screw 6 is closed and sealed bythe O-ring 7 when the proper volumes of fluid and air are provided bythe molded shape of the bladder.

Since the fluid system has no air in it, the bike can be bounced, laidon its side and turned upside down with no air ingestion problem orother negative effects that would be suffered by traditional reservoirtype master cylinders or other so-called systems.

Referring to FIGS. 2 and 2A and particularly to a lever 23 which ispivotally connected to the housing 2 by means of a pivot pin 24. In thisregard a push rod 25 interconnects the lever 23 to the piston 9. A stopflange 26 is provided on the rod 25 and a slot 27 is formed on the outerend of the push rod 25. An adjustor bushing 28 is provided on the outerend of the push rod 25. A ball 29 is provided on the other end of thepush rod 25 which is seated in a piston socket 30 as shown in FIG. 2A.Piston socket snap fit beams 31 are provided around the ball 29 andretained therein by the snap ring 32.

The lever position adjustment as shown in FIG. 2B is accomplishedwithout affecting the critical clearance 33 between the primary seal at10 and the timing port 11 as shown in FIG. 2B. The push rod 25 can berotated by a screw driver aligned with slot 27 at the end of the rod 25.As the rod 25 is rotated the adjustor bushing 28 travels down the rod25, moving the lever 23 with it. The most extreme adjustments arelimited by flange 26 formed on the rod 25 in one direction and the screwslot 27 entering the adjustor bushing 28 in the other direction.

The lever 23 maintains its adjustment through a friction hold. Theadjustor bushing's first thread is an interference thread to the rod 25.A boot 64 is tightly mounted on the rod 25 and the outer end of thecylindrical body 4 to enclose the open end of the cylindrical body 4.

The piston 9 is prevented from exiting the bore 35 by means of the snapring 32 which is retained in a groove 36 in the end of the cartridgebody 4. The rod 25 is kept from being loose in the piston 9 by the useof the resilient piston material whose snap joint beams 31 are sprung tointerfere with the rod ball end 29 as shown in FIG. 2A. The rod ball end29 is prevented from exiting the piston by the beams 31 that will notopen wide enough to allow the rod ball end 29 to escape due to contactwith the beams 31. Therefore, in the free state the rod 25 can besnapped into the piston 9. Removal of the rod ball end 29 from pistonsocket 30 is prevented by the restriction of movement the beams 31provide.

In FIGS. 4, 5 and 6 brake caliper housings 17 and 17' are shown havingangularly machined seal grooves 18 and 18', an undercut bore 19 and apiston 20 in each bore 19. The engagement length of the pistons 20 tothe bore land area 21 is made to be extremely short so as to allow thepistons to be angularly offset as shown in FIG. 4. This allows thepistons 20 to be designed with a length adequate only for sealing thepiston 20 through the full cycle of a friction pad's wear as shown inFIG. 6 rather than needing a longer engagement as shown in FIG. 5 toresist jamming by sticking in the bore. This shortens the necessary boredepth 22 and allows for a greater spoke angle x of the wheel as shown inFIG. 6 than at the spoke angle x' of FIG. 5. This allows for a wheelwith greater lateral strength which is important in rough riding. Thepiston and bore design also allows for smaller, lighter parts which isimportant for human powered vehicles.

Referring to FIGS. 7, 8 and 9, a friction pad and plate assembly 38 isshown which includes a backing plate 40 having a tab 46 for insertingand removing the assembly 38 from the piston 20. A friction pad 41 isformed on one side of the backing plate 40. A flexion spring 42 ismounted on the plate 40. The spring 42 includes a hook 80 on each endwhich snaps onto ears 81 on the plate 40. A U-shaped loop 55 is providedintermediate the ends of the spring 42 and an offset section 82 on eachleg of the spring which is aligned with a groove 60 in the plate 40. Inthe installed condition the plates 40 are held snugly against thepistons 20 by the springs 42.

A piston post 47 is partially embedded in each of the pistons 20. A cap61 is provided on the end of the post 47. The friction pad and plateassembly 38 is connected to the piston 20 by sliding the plate assembly38 upward so that the U-shaped loop 55 engages the post 47 and isretained thereon by cap 61. A recess 43 is provided in the plate 40which is aligned with the post 47 on the piston 20. The plate assembly38 is positioned on the piston 20 by sliding the plate assembly 38 intothe slot 45 with the U-shaped loop 55 aligned with the cap 61. The tab46 is lifted as shown in FIG. 11. The spring 42 is deflected and thepiston post 47 is clear of the friction pad plate hole edge 44. Thefriction pad and plate assembly 38 can be slid out of the bottom of thecaliper housing as shown in FIG. 13. This is the only avenue of escapefor the pad as the other three sides are closed.

During insertion of the pads as shown in FIG. 12, the left side of thefriction pad and plate assembly 38 is slid up until a beveled section 83of the plate 38, ramps over the piston post 47. The post 47 engages thespring 42, deflecting it away from the backing plate 40. The plateassembly 38 continues sliding until the U-shaped loop 55 snaps over thepost 47. The pad is then pulled into contact with the piston face byspring 42 and the recess 43 captures the piston post 47. Once the wheeland disk assembly 39 of the bicycle are reinserted into the forks 84,the pads are trapped from lifting out of piston engagement and thuscannot escape.

A thermally compliant lightweight brake disk 59, as show in FIG. 14, isdesigned to prevent yielding which can cause warping or fracture undercombined thermal and high torque loading. A friction contact ring 85 issupported by a number of curved legs 57 which are formed in a circulararea 58. The legs 57 are shaped in such a way as to bend to comply withthe outer ring's desire to expand when heated. This prevents high stressconcentration on the legs 57 and avoids yielding. The legs 57 are alsodesigned to be strong enough to withstand exceptionally high brakingtorque. Finally, the legs 57 are shaped to provide adequate axialbending but strength enough to prevent impact damage. It is importantthat the disk remains flat when not in use.

Referring to FIG. 15 a fixed mount single acting caliper 86 is shownmounted on the bicycle frame in a position to straddle the lightweightbrake disk 59. The caliper 86 is set up on the frame with a clearance of0.010 inch between fixed pad 87 and the disk 59. The brake actuator 66is positioned on the mount side with the moveable pad 88 positioned toengage the disk 59 after 0.010 movement. When the brake actuator 66 isapplied, the moveable pad 88 closes the 0.010 gap, contacts the ring 85,flexes the ring 85 into contact with the fixed pad 87 and progressivefrictional clamping occurs. Upon release of the moveable pad, the ring85 returns to its home position with a clearance of 0.010 inch betweenthe ring 85 and the fixed pad 87 and between the ring 85 and themoveable pad 88. With this arrangement, zero drag is provided on eachside of the disk due to its flexibility and the resultant clearance.

Thus, it should be apparent that there has been provided in accordancewith the present invention a bicycle brake system that fully satisfiesthe objectives and advantages set forth above. Although the inventionhas been described in conjunction with specific embodiments thereof, itis evident that many alternatives, modifications and variations will beapparent to those skilled in the art. Accordingly, it is intended toembrace all such alternatives, modifications and variations that fallwithin the spirit and broad scope of the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A hydraulic brake systemfor a two wheel bike having a handlebar comprising:a master cylinderassembly mounted on the handlebar, said master cylinder assemblyincluding:an outer housing, a tubular cartridge body mounted in theouter housing, a master piston mounted in the cartridge body, anoperating lever pivotally mounted on the outer housing, a push rodoperatively connecting the operating lever to the master piston, aspring mounted in the cartridge body to bias the master piston to aninoperative position in the cartridge body, a resilient bladderenclosing the cartridge body, a hydraulic fluid in said bladder, a porttiming hole in said cartridge body operatively connecting the cartridgebody to the bladder to maintain fluid in the cartridge body, a brakeassembly mounted on a caliper housing and a brake line operativelyconnecting the cartridge body to the brake assembly.
 2. The hydraulicbrake system according to claim 1 wherein the master cylinder assemblyincludes means for adjusting the operating lever position with respectto the master piston to compensate for variable size operators.
 3. Thehydraulic brake system according to claim 2 wherein said adjusting meanscomprises a threaded push rod operatively connected to the master pistonand a threaded adjuster bushing pivotally mounted in the operating leverto adjust the position of the operating lever without affecting themaster piston position.
 4. The hydraulic brake system according to claim3 wherein the master cylinder assembly includes bleeder means forventing air from the bladder.
 5. The hydraulic brake system according toclaim 4 wherein said bladder is provided with dimples in the sides ofthe bladder to allow for expansion and contraction of the hydraulicfluid in the bladder.
 6. The hydraulic brake system according to claim 3wherein the master cylinder assembly includes a boot mounted on the pushrod and an outer end of the cartridge body to enclose the outer end ofthe cartridge body.
 7. The hydraulic brake system according to claim 1further comprising a brake disk mounted on one of the wheels, thecaliper housing mounted on each side of the brake disk, a brake pistonmounted on each side of the brake disk, a friction pad and plateassembly mounted on each of said brake pistons in a spaced relation tothe brake disk.
 8. The hydraulic brake system according to claim 7wherein a piston post and cap is mounted on each of said brake pistonsand one of said friction pad and plate assemblies is mounted on each ofsaid piston posts.
 9. The hydraulic brake system according to claim 8wherein said friction pad and plate assemblies each include a flexionspring for engaging each of said piston posts.
 10. The hydraulic brakesystem according to claim 7 wherein the brake disk comprises an outerfriction contact ring supported by a plurality of curved legs, thecurved legs being shaped to bend in compliance with expansion of theouter friction contact ring which occurs when the outer friction contactring is heated.
 11. A hydraulic brake system for a bike having ahandlebar and a pair of wheels, the system comprising:a master cylinderassembly adapted to be mounted on the handlebar, said master cylinderassembly including an outer housing, a cylinder having one end mountedin the outer housing, a master piston mounted in the cylinder, aresilient bladder having one end mounted on the outer housing and theother end mounted on the cylinder, the resilient bladder forming a fluidreservoir, wherein the cylinder has a port timing hole operativelyconnecting the cylinder to the bladder to maintain fluid in the cylinderto self adjust for pad wear, and a bleeder valve in the outer housing tovent air out of the bladder, wherein said port timing hole is closedwhen the master piston is actuated to apply a brake assembly.
 12. Thehydraulic brake system according to claim 11 further comprising a brakedisk mounted on one of the wheels, a caliper housing mounted on eachside of the brake disk, a brake piston mounted on each side of the brakedisk, and a friction pad and plate assembly mounted on each of saidbrake pistons.
 13. The hydraulic brake system according to claim 12wherein a piston post is mounted in each of said brake pistons and saidfriction pad and plate assemblies are mounted on said piston posts. 14.The hydraulic brake system according to claim 13 wherein said frictionpad and plate assemblies each include a flexion spring for engaging oneof said piston posts.
 15. The hydraulic brake system according to claim12 wherein the brake disk comprises an outer friction contact ringsupported by a plurality of curved legs, the curved legs being shaped tobend in compliance with expansion of the outer friction contact ringwhich occurs when the outer friction contact ring is heated.